1. Field of the Invention
The present invention relates to a surface-treating apparatus for blanks for can bodies used as in beverage cans and the like, and specifically to a surface-treating apparatus for blanks for can bodies used in welded cans.
2. Description of the Related Art
As metal cans used as containers for beverage, there have been known cans obtained by welding both end edges of a strip-like blank to each other to form a can body and double-seaming individual can ends to both ends of the can body.
In order to prevent the corrosion of a base metal due to the contact of the base metal with the contents in the can and the change in the flavor of the contents, which is caused by metal components being dissolved, the cans as described above have heretofore been coated with a coating material such as an epoxy-phenol resin on the inside thereof. On the other hand, coating has been conducted on the outside of the cans to impart a good aesthetic appearance. In such cans, baking has been carried out in a heating oven whenever coating was completed on each side of the base metal. Therefore, heat and vaporized organic solvents have a tendency to impair the working environment.
There is thus a demand for covering both sides of the base metal with a polyester film. Such covering makes it unnecessary to conduct the coating and baking and hence can be expected to improve the working environment.
According to cans obtained by covering a side of the base metal, which is to be the inside of the cans, with a polyester film, the corrosion of the base metal can be prevented, and moreover the flavor of the contents in the cans can be protected from changing due to the resin being slightly dissolved out of the coating film in the can whose inside has been coated with the resin as described above. According to cans obtained by covering a side of the base metal, which is to be the outside of the cans, with a printed polyester film, on the other hand, a good aesthetic appearance can be given to the outer surfaces of the cans without conducting coating.